Since the establishment of a networked computing, a variety of image data is now frequently transmitted among a plurality of computers. Accordingly, demand for capturing various image data for the computers is increasing. Generally, when image information is taken into a personal computer, an add-in video capture board is mounted on the computer, and image information supplied through a video camera or electronic still camera connected to the add-in board is converted into a predetermined data format before sent to the computer. Image data captured by the computer is temporarily stored in the internal storage device and can be transmitted to other computer equipment through the network as required.
FIG. 1 is a schematic diagram showing an example configuration of a network system. This drawing shows a client/server type network system.
Communication line L comprises a coaxial, twisted pair, or fiber optic cable. A server C0 and a plurality of clients C1 to C5 are connected to the communication line L. The server C0 performs a variety of processing in response to requirements from the clients C1 to C5 and also manages operation of the network system as a whole. The clients C1 to C5 operate independently and transfer a variety of data to/from the server C0 or another one or more of the clients C1 to C5 as required.
The server C0 and the clients C1 to C5 are given respective unique network addresses, and the server C0 or the clients C1 to C5 are configured so to be mutually identifiable based on these network addresses. Each of the clients C1 to C5 can share data or a variety of hardware with the server C0 or another one or more of the clients C1 to C5.
The clients C1, C4 have respective cameras V1, V2 as input device of image data so to enable capturing image data. Image data taken into the clients C1, C4 through the cameras V1, V2 is temporarily stored in a storage device such as a hard disk in the clients C1, C4. The image data is transferred to any of the clients C1 to C5 or the server C0 as desired in response to a transfer requirement from any one of the clients C1 to C5. The image data is transferred on a picture-by-picture basis, or in units of divided blocks of each picture, according to the communication protocol of the network system.
Where it is determined that cameras V1, V2 will be shared over the network, the clients C2, C3, C5 not having the cameras V1, V2 can control the cameras V1, V2 via the clients C1, C4. Image data is transferred in the same way as above, either on a picture-by-picture basis, or in units of divided blocks, again, according to the network communication protocol.
FIG. 2 is a block diagram showing the configuration of a video capture for capturing image information taken into a client (personal computer) by an electronic camera. The drawing shows that the image information is output as digital data (image data) from the electronic camera.
A capture board 10 comprises a frame memory 1, a synchronism detecting circuit 2, a timing control circuit 3, and an interface circuit 4, and is connected between the electronic camera and a client. The frame memory 1 stores image data, input through the electronic camera on a picture-by-picture basis. This frame memory 1 has sufficient capacity to store a number of pictures according to a ratio between an input rate of image data from the electronic camera and a transfer rate of image data to the client. The synchronism detecting circuit 2 detects a synchronism component contained in the image data entered from the electronic camera and generates a timing pulse corresponding to each timing of vertical scanning and horizontal scanning. The timing control circuit 3 controls timing of writing and reading image data into and from the frame memory 1 based on the timing pulse supplied from the synchronism detecting circuit 2 and directions from the client.
An interface (I/F) circuit 4 is connected between the frame memory 1 and the client and transfers image data read from the frame memory 1 to the client according to the instructions given by the timing control circuit 3. The interface circuit 4 sends interrupt instructions being output from the timing control circuit 3 to the client, receives a control command sent out from the client, and then gives instructions to the timing control circuit 3. Thus, the image data input from the electronic camera on a picture-by-picture basis is stored in the frame memory 1 on a picture-by-picture basis and also taken into the client on a picture-by-picture basis in response to a request from the client.
Control programs corresponding to the cameras V1, V2 and their video captures are installed in the clients C1, C4 connected with the cameras V1, V2. The cameras V1, V2 are connected to the clients C1, C4 and can only be controlled by the clients C1, C4. When the clients C2, C3, C5 to which the cameras V1, V2 are not connected, wish to capture image data using the cameras V1, V2, image data must first be sent to the clients C1, C4 which are connected with the cameras V1, V2 before it can be transferred from the clients C1, C4 to the clients C2, C3, C5. Where the cameras V1, V2 are shared on the network, the control programs are installed in the clients C2, C3, C5, so that the cameras V1, V2 can be controlled from the clients C2, C3, C5 of the network via the clients C1, C4.
In such a network, the cameras V1, V2 are connected to the communication line L via respective clients C1, C4. In other words, the clients C1, C4 are necessary in order to connect the cameras V1, V2 to the network. If the clients C1, C4 connected with the cameras V1, V2 are not turned on, the operation of the cameras V1, V2 cannot be controlled, regardless of the control programs installed in the other clients C2, C3, C5. Therefore, topological placement of the cameras V1, V2 is limited to the neighborhood of the clients C1, C4, and their versatility is lowered. As a result, the cost of the network system increases.